The present invention relates to the field of chains used in conveyors for industrial processes such as ovens for sealing the frit glass of cathode ray tubes. More specifically, the present invention relates to a device and method for separating the links of such chains when necessary for repair or maintenance. The present invention also relates to a device and method for reassembling the links of such chains.
Many industrial processes require the movement of articles along an assembly line. Additionally, some industrial processes require the movement of articles through a processing device, such as an oven, inspection station or washing machine. A specific example of such a process is the manufacturing of cathode ray tubes. Cathode ray tubes are typically used to construct televisions and computer monitors.
In cathode ray tube manufacture, a relatively flat portion of the tube, i.e., the face portion where images are displayed, is attached to a funnel and neck portion that extends away from the face. Frit glass is used to create the seal between the face portion and the funnel portion of the cathode ray tube. After the frit is applied, the assembly is baked in an oven to solidify the frit glass and create the seal between the face and funnel portions of the cathode ray tube.
In conventional cathode ray tube manufacturing, a conveyor consisting of driven chains is used to transport the tubes through a frit sealing oven. The chains are designed to be extremely strong and capable of withstanding the drastic variations in temperature experienced passing into and through the frit sealing oven. Such a chain drive system is being incorporated into the majority of new frit sealing oven designs.
FIG. 1 includes a top and side view of a typical chain used in such industrial processes as cathode ray tube frit sealing ovens. As shown in FIG. 1, the links of the chain (100) are made by rectangular metal plates (101) which are connected by interference-fit connecting pins (102). Two plates (101), an upper plate (101A) and a lower plate (101B), run between each pair of adjacent pins (102A, 102B) to form a link in the chain (100).
The distance between the upper and lower plates (101) alternates with every other link of the chain (100) as shown in FIG. 1. Each pin (102) passes through four plates (101), thereby securing an inner (101C) and outer (101A, 1010B) pair of plates (101). These inner and outer plate pairs correspond to different links in the chain (100) as shown in FIG. 1.
Each connecting pin (102) also passes through a roller (103)that rotates freely about the pin (102) and maintains the separation between the plates (101) attached to that pin (102). A side view of the chain (100A) shows that the rollers (103) extend below the plates (101) to allow the chain to roll. This effect is achieved by shift the holes in the plates (101), through which the pin (102) passes, downward from the center line of the plate (101).
Shifting the rollers (103) downward to extend below the chain (101) also leaves a relatively flat upper surface of the chain (101). This surface is well-suited for transporting product fixtures such as cathode ray tube assemblies.
The connecting pins (102) are interference-fit through holes in the plates (101). The interference-fit is, for example, a 10-ton press. This is necessary in order to hold the chain together under the extreme temperature variations and load that the chain is subjected to. The conventional method of assembling the chain (100) is to drive the pins (102) through the chain plates (101) with a sledgehammer. For added security, a cotter pin (104) is then inserted through a hole in the end of each pin (102).
While these conveyor chains (100) are extremely strong and capable of standing up to the extreme conditions of industrial processes, the strength of the chains (100) also poses problems. For example, portions of the chain are subject to wear, for example, the rollers (103). However, when the chain becomes worn and needs to be replaced or requires maintenance, there is no way to disassemble or break the chain (100).
The use of conveyor chains (100) using interference-fit pins (102) in industrial processes is relatively new. Consequently, the manufacturers of these conveyor chains provide no method or device breaking or disassemble the chain (100) when necessary to replace or repair it. Moreover, once the chain (100) is installed there is typically very little space available to physically work on the chain (100). This prevents any large device from being used to separate the links of the chain (100). Additionally, the offset roller (103) and pin (102) preclude the use of a symmetrical-style press, for example, in disassembling the chain (100).
Consequently, there is a need in the art for a device and method for disassembling a conveyor chain which is linked with interference-fit pins so that the chain can be replaced or serviced. There is a further need in the art for a device and method of assembling or re-assembling such a chain.
It is an object of the present invention to meet the above-described needs and others. Specifically, it is an object of the present invention to provide a device and method for disassembling a conveyor chain that is linked with interference-fit pins so that the chain can be replaced or serviced. It is a further object of the present invention to provide a device and method of assembling or re-assembling such a chain.
Additional objects, advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The objects and advantages of the invention may be achieved through the means recited in the attached claims.
To achieve these stated and other objects, the present invention may be embodied and described as a hydraulic press for disassembling a conveyor chain that has interference-fit connecting pins between chain links. The press includes a hydraulic unit with a hydraulic head; and a structure for clamping the hydraulic unit to the conveyor chain such that the hydraulic head, when actuated, forces one of the interference-fit connecting pins at least partially out of the conveyor chain to disassemble the conveyor chain.
The clamping structure preferably includes aback plate; a cylinder plate on which the hydraulic unit is mounted; and a number of bolts connecting the back plate to the cylinder plate. This structure is clamped to the conveyor chain by tightening the bolts between the back plate and the cylinder plate when the chain is disposed between the back plate and the cylinder plate.
The press also preferably includes a spacer plate that is in contact with both the back plate and an inner plate of a first chain link of the conveyor chain. The spacer plate allows the back plate to rest evenly on an outer plate of a second chain link adjacent the first chain link and the spacer plate.
In order to disassemble the chain, the back plate may have a hole through which the connecting pin passes when forced from the chain by the hydraulic head. Preferably, this hole is offset from a center of the back plate to account for a corresponding offset of the connecting pin from the center-line of the chain.
The present invention also encompasses the method of using the press described above. Specifically, the present invention encompasses a method of disassembling a conveyor chain with interference-fit connecting pins between chain links by clamping a portable hydraulic unit with a hydraulic head to the conveyor chain such that the hydraulic head, when actuated, forces one of the interference-fit connecting pins at least partially out of the conveyor chain to disassemble the conveyor chain.
The present invention also encompasses the method of suing the press described above to assemble or reassemble the chain. Specifically, the present invention encompasses a method of assembling a conveyor chain with interference-fit connecting pins between chain links by clamping a portable hydraulic unit with a hydraulic head to the conveyor chain such that the hydraulic head, when actuated, forces one of the interference-fit connecting pins into the chain to assemble the chain.